Compressor



8% 150 A. TRASK 50 376 COMPRESSOR Filed Des. 13, 1945 2 Sheets-Sheet 1 A. TRASK 2,509,376

COMPRESSOR 2 SheetsSheet 2- M m mm Filed Dec. 15, 1945 M W wy Patented May 30, 1950 UNITED STATES TENT OFFICE 1 Claim.

This invention relates to gaseous fluid compressors, particularly of the rotary type wherein compression is effected by centrifugal force acting upon the fluid being compressed.

The compressor herein described may be regarded as a multi-stage centrifugal compressor wherein the compression stages are arranged in series substantially radially of the compressor rotor as contrasted with the usual type of such device wherein the compression stages are disposed in series axially of the rotor.

Among the principal objects and advantages of the invention it is intended to provide an effective compressor having a minimum number of moving parts and one that is simple to produce at low cost where only a minimum amount of machining is required. The present device comprises a multi-stage centrifugal compressor providing a single pass radial flow of fluid from an internal central portion of the compressor rotor to the periphery thereof.

The foregoing constitutes some of the principal objects and advantages of the present invention, others of which will become apparent from the following description and the drawings, in which,

Fig. l is a vertical sectional view throu h a compressor embodying the present invention, the rotor being shown in section taken on the line l--l of Fig. 2;

Fig. 2 is a vertical sectional view through the rotor of Fig. 1, the view being taken on the line 22 of Fig. 1;

Fig. 3 is a side elevational view of the rotor shown in Fig. 2, the view showing the complete rotor however, rather than merely that portion as shown in Fig. 2;

Fig. 4 is a transverse sectional View through the rotor, the view being taken on the line 4-4 of Fig. 2;

Fig. 5 is a View corresponding to Fig. 3, but showing a plurality of compression discs of the type shown in Fig. 6;

Fig. 6 is a perspective view showing a modifled form of a compression disc;

Fig. 7 is an enlarged, fragmentary sectional view through the compression disc of Fig. 6, the view being taken on. the line 11 of Fig. 6;

Fig. 8 is a sectional view taken through a rotor illustrating a modified form of the invention; and

Fig. 9 is a perspective view of the sintered metal insert of Fig. 8, with a portion broken away.

For purposes of illustration specific embodiments only of. the invention are shown and described. It is recognized however, that many modifications will occur to the man skilled in the art and it is intended that such modifications may be made without departing from the intended scope of the invention.

This invention comprises a centrifugal compressor rotor of novel construction. The rotor has a central inlet opening for the fluid to be compressed and is provided with radial passages extending from this central opening for conducting and at the same time compressing the fluid to be compressed. These passages are formed by a multitude of interconnecting openings or interstices between sintered particles of metal or between the strands or threads of wire mesh or glass cloth or the like, and the general direction of flow of fluid from the central opening to the periphery of the rotor is radially. This fiow of fluid is brought about by rotating the rotor at a high velocity so as to throw the fluid by centrifugal force in a direction toward the periphery of the rotor. While the fluid is directed through the multitude of small passages it is compressed so that the fluid leaving the periphery of the rotor is at a pressure in excess of that entering the central openingin the rotor.

Referring now to the drawings and particularly to Fig. 1, one embodiment of the invention is shown and comprises a compressor housing l5 in which is mounted a shaft l6 that is journaled at I! and [8. The shaft it supportsa rotor generally indicated at I9.

The housing i5 is provided on one Wall with an outwardly projecting boss 20 that is apertured as at 2! to receive an inlet tube or pipe 22 threaded into the aperture 2| as at 23. Extending inwardly from the same wall of the housing i5 is the journal bearing ii. A passage :25 projects through the boss 20 in alignment with the internal opening in the journal bearing Ill.

Projecting outwardly from the opposite wall of the housing I5 is a boss 25 that is hollow to provide a chamber 26. This chamber is closed by a removable plate 27. fastened as at 28 by means of screws or the like to the boss 25. A gasket 29 is inserted between the cover plate 2'6 and the boss 25. The journal bearing iii is formed on this last mentioned wall of the housing !5.

The shaft I6 is provided at one end with a longitudinal passage 35 that extends throughout a portion of its length. At the opposite end of the shaft a shoulder at is provided. and the shaft projects through an opening 32 in the cover plate 2?.

Between the shoulder 31 of the shaft l6 and.

the cover plate 21 is a sealing member generally indicated at 33 that includes a pair of annular members 34 and 35 that are adapted to rotate with respect to each other, a rubber gasket like member 35 that effectively seals the opening through the cover plate 2? and a second rubber gasket 31 that rests between the shoulder 3i and a tapered face 38 on the annular member 35. This sealing member as serves to prevent leakage through the passage in the cover plate 2'! and also aids in maintaining the proper position of the shaft it as will be brought out presently. For further details of the specific construction and operation of this sea-ling member 53, reference may be had to Patent No. 2,245,106 which relates specifically to this member.

At the opposite end of the shaft it is provided a spring seat portion 39 that is adapted to receive a compression spring ltl that is held between this seat portion 35 and a ball ii. A plug 42 is threaded into the Opening 25 against the ball 4| and by adjustment of this plug 52, more or less compression in spring it can be provided so as to properly position the shaft 58 with respect to the sealing member 33. It is important that sumcient pressure be exerted at all times by the spring Ell against the shaft it in a lengthwise direction thereof so as to make the sealing member 33 effective.

The rotor l9 comprises a pair of face plates 43 and 44 that sandwich therebetween a disc-like member 45, which may be referred to as an insert. This assembly comprising the face plates at and 44 and the disc-like member s is held together by a plurality of bolts and nuts indicated at 46.

'The face plates 43 and M are provided with hub portions ll and i8 respectively for fluid tight mounting on the shaft it. The rotor may be fixed to the shaft it by means of a pressed fit and locked by means of a suitable machine screw 49 that passes through the hub portion All and is recessed into a depression in the shaft E6.

The disc portion 65 of the rotor 59 may be a separate member as shown for example in Fig. 6, or it may be formed as an annular series of inserts in depressions within one or both of the face plates it and id as illustrated in Figs. 2 and 3. In this latter form as shown in Fig. 3, face plates 43 is provided with grooves fill that extend radially from a central opening 5! (Fig. 2) to the periphery of the face plate. These grooves 50 are shown in Fig. 2 as being disposed about the circumference of the face plate, more or less in the form of a six-pointed star. Each groove 56 is filled with an insert 52 of material such as wire mesh, glass cloth woven from glass fiber, or sintered metal particles, all of which materials provide a plurality of cavities or interstices that are more or less interconnected. As shown in Fig. 3 the face plate 44 is provided with projecting portions 53 that correspond in shape with the grooves 5t on the face plate t3 and when the face plates 43 and as are bolted together as shown in Fig. 3, these projections 53 fit into the grooves 50 so as to provide radial slots in which the inserts 52 are held. Thus a multitude of small tortuous passages are provided from the central opening 5| of the rotor IE] to the periphery of the rotor through the inserts 52.

In Fig. 6 the compression disc 45 is shown as a separate element and comprises a sheet of wire mesh in the form of a circular disc that has vulcanized thereto a plurality of pie-shaped rubber elements M that are spaced about the periphery of the wire mesh so as to provide a plurality of tapered radial passages 55. As shown in Fig. 6 the wire mesh is vulcanized into the body of the rubber elements 54 but in the areas between the rubber elements 54 the passages 55 that are formed are filled with wire mesh as indicated at 56. This disc 45 is then sandwiched in between face plates, which in this instance are identified at 43a and 44a. A plurality of bolts 46a passing through perforations 51 in the disc -45 firmly hold the disc between the face plates 43a and 44a as shown in Fig. 4.

It may be desirable to provide a plurality of discs 45 as shown in Fig. 5 in which case spacers 58 separate the discs 45 from each other.

In Fig. 8 another embodiment of the invention is shown where the central disc 45 is in the form of a ring 59 of sintered metal particles, sponge plastic or the like. The side faces of this ring are tapered as shown at 80. Face plates 6! and 62 having annular faces E53 and 64 respectively cooperate with the tapered faces on the ring member 50 when the unit is assembled as shown in Fig. 8. Gaskets 65 may be inserted between the sides of the ring member 59 and the cooperating faces of the face plates BI and 52. Thus a plurality of tortuous passages between the sintered particles of metal in the ring 59 provide paths for a fluid to pass from the central periphery thereof.

As previously mentioned in connection with Fig. 1, the shaft 15 is hollow as at 3B for a portion of its length, this hollow portion terminating adjacent to the central opening 5| of the rotor Iii. Radial passages 66 project through the wall of the shaft it from the hollow portion 30 thereof to the periphery, thereby providing communication with the central opening 5! of the rotor 59 (see Figs. 1 and 8).

Again referring to Fig. 1 an outlet passage 61 is provided in the compressor casing for conducting compressed fluid from the discharge side of the compressor. A lubricant indicated at 68 may be provided in the bottom of the casing i5 and a pipe 69 may be utilized to conduct lubricant to the bearing member l1.

As previously mentioned a chamber 26 is provided in the boss 25 and this chamber may be filled with a lubricant that is drawn from the supply 68 at the bottom of the compressor housing it through an intake pipe 10. About the periphery of the shaft I6 is disposed a helical groove H that at one end communicates with the supply of lubricant in the chamber 26 and at the other end communicates with a. passage l2 that is disposed along the central line of the shaft [6 and is in communication with the hollow portion 30 of the shaft it. Lubricant is fed through this helical passage H by virtue of the suction that is created in the hollow portion 39 of the shaft I 6. This suction is the result of the pressure difference between the suction and discharge sides of the compressor. In this manner bearing portion i8 is lubricated; A sintered metal [plug 13 may be inserted in passage 12 to control the rate of flow of oil.

It can thus be seen that rotor 19 is provided with a multitude of small tortuous passages extending from the central part of the rotor to the periphery thereof. These passages are either provided in closely fitting inserts of porous ma-' terial, such as that illustrated in Figs. 2 and 3, or they may be provided in the manner illustrated in connection with Fig. 6, or in a ring or doughnut-shaped member as illustrated in Fig. 8.

The passages themselves are formed by the interconnected cavities or interstices between the wire or thread-like members illustrated in Figs. 2 and 6 or between particles of metal, such for example as nickel or steel that are sintered together as illustrated in Fig. 8. These tortuous passages extend generally from the center of the rotor to the periphery, and may be provided in such other material as glass wool, sponge rubber, sponge plastic or wire cloth. In each of the examples shown, the members in which these minute passages are disposed are tapered from a maximum transverse area at the internal opening or chamber in the rotor to a smaller transverse area at the periphery of the rotor, said taper being of a nature to compensate for the reduction in fluid volume and increase in fluid viscosity during compression of the fluid.

The rotor I9 is caused to rotate with the shaft it by a motor or the like (not shown) and gaseous fluid such as Freon enters the hollow portion 30 of the shaft 16 through the inlet pipe 22. This fluid from the hollow portion 38 of the shaft passes out through radial slots 66 into the central opening 5| of the rotor and by centrifugal force is thrown radiaily into the minute passages that extend to the periphery of the rotor. This fluid enters the minute tortuous passages and is forced in a general radially direction from the central opening 5| in the rotor toward the periphery thereof.

The gaseous fluid thus flowing radially outwardly from the central portion of the rotor through the porous inserts, such for example as the inserts 52 in Fig. 2, or through the porous doughnut-shaped member 59 shown in Fig. 8, accumulates different increments of pressure induced by centrifugal force as it passes in series from one internal cavity to the next through the connecting openings. These successive cavities provide in effect successive stages, each having a higher fluid pressure within than the next adjacent cavity that is disposed toward the center of the rotor. If a layer of 150 mesh wire cloth were used as an insert two inches long radially, with the weave at right angles to a rotor radius, then, in effect, the fluid being compressed would pass through 300 stages of pressure increase in its travel from a central rotor cavity radially through the wire cloth insert. If the pressure gain increment is one half pound at each stage, then the pressure capacity of the compressor would be approximately 150 pounds per square inch. If sintered powdered metal be used for rotor inserts, a greater number of internal cavities per lineal inch is provided and thus a greater number of compression stages is had, each adding its pressure to a total compressor pressure proportional to the number of stages provided.

A compressor comprising this invention is constructed to provide for fluid intake within an internal central portion of the rotor and a discharge from the periphery of the rotor into a surrounding high pressure chamber through porous inserts of a nature above described. Rotor inserts are selected of such porosity that their resistance to fluid flow will maintain the fluid pressure difference required of the compressor during compression, during the time the volume of flow is maintained at the required delivery volume of the compressor. The pressure-volume flow characteristics of inserts may be tested for suitability in the following manner:

If air is the fluid to be compressed, the compressor to be tested has its high pressure discharge opening connected to a source of compressed air ata pressure equal to the pressure desired as the capacity of the centrifugal compressor. A test fluid pressure gage is connected for indicating the air pressure within the high pressure chamber of the compressor. An air flow meter is provided with its inlet connected by a conduit to the suction opening of the compressor to be tested. This low pressure conduit is connected to a pressure gage for indicating the air pressure at the compressor suction inlet. A throttle valve is provided to regulate the volume and pressure of air flow into the flow meter.

The test is started by opening a flow of compressed air into the compressor. On the high pressure gage the air pressure is checked against that pressure desired as the capacity of the compressor. The throttle valve is set to effect a pressure in the low pressure line equal to that required as the standard suction pressure for the compressor. If the normal suction pressure for the compressor is atmospheric, then the throttle valve is left open. The volume of air flow is then measured at the flow meter. If the volume of air flowing is greater than that desired as the capacity of the compressor, then rotor inserts of a reduced transverse area and/or a reduced porosity size are required. If the test volume of air flowing is less than that desired as the capacity of the compressor, then rotor inserts of an increased transverse area and/or increased porosity size are required.

When rotor inserts of suitable pressure-volume flow characteristics have been selected by the above method of testing, then their effectiveness in the compressor structure may be tested in the following manner:

Air compressed to the desiredcompressor suction pressure is delivered by a conduit to the suction opening of the compressor. If the compressor is to normally take air for compression at atmospheric pressure, then its suction opening is left open. A test pressure gage is connected to the high pressure chamber of the compressor. A throttle valve is connected to the discharge openin of the compressor and a conduit is connected from said throttle valve to an air flow meter. The compressor is then connected to a variable speed motor provided with a tachometer.

The compressor is then operated at the lowest speed that will produce the desired volume of air flow when operating against the desired head pressure. The throttle valve in the compressor discharge line is regulated to maintain the required discharge pressure during the testing.

It is usually desirable to have centrifugal compressors operate at one of the standard speeds of induction motors; 1725 R. P. M. or 3400 R. P. M. If the compressor being tested requires an R. P. M. faster than that desired to maintain its rated capacity, then the said porous rotor inserts should be constructed to have a finer porosity and/or a smaller size series of interstices with a proportionately increased transverse area to give equal pressure-volume flow results in the original test above set forth. If the compressor being tested requires an R. P. M. slower than that desired to maintain its rated capacity, then the said porous rotor inserts should be constructed to have a coarser porosity and/or a larger size series of interstices with a proportionately decreased transverse area to give equal pressure-volume flow results in the original test above set forth.

The compressor speed required for a given can pacity may be reduced by increasing the diameter of the rotor and maintaining the same pressure-volume flow results through the porous inserts. Inversely the compressor speed may be increased by reducing the diameter of the rotor while maintaining the same pressure-volume flow characteristics of the inserts.

When it is desirable to have compressor lubricating oil flow in a circuit requiring its passage through the rotor of the compressor, then the design and shape of the porous rotor inserts must be such as to accommodate the required flow of oil along with the flow of gaseous fluid through the radial passages of the rotor. The size and nature of the porosity and associated interstices must be such as to accommodate the presence of flowing lubricating oil while the desired pressure-volume fluid flow characteristics of the porous inserts are maintained. Also the taper and shape of the inserts must conform to this circumstance.

Centrifugal compressors constructed in accordance with this specification may be built in all fractional horsepower motor sizes and in any desired integral horsepower size as well. They may be constructed either of the hermetically sealed type or of the conventional open type using a shaft seal. They may be used in refrigeration systems to compress refrigerant vapors such as Freon, methyl, chloride, or ammonia, or they may be designed for compressors of air or other gaseous fluids. Any of these various types of centrifugal compressors may be constructed with capacities throughout a wide range of suction pressures and discharge pressures to meet all the usual requirements for fluid compressors.

Thus a novel compressor is provided. This unit may be employed as a compressor for refrigeration purposes and the like as the only compressor unit in the system or the device may be utilized as a supercharger in conjunction with a second compressor that may be in the form of a rotary or reciprocating compressor that has its intake connecting to the discharge or high pressure side of the device disclosed herein.

It will be readily understood by those familiar with the art that two or more compressor rotors comprising this invention may be assembled to rotate on a common shaft and interconnected in axial series to effect a series of successive pressure stages in the conventional manner. Such compressor would compress fluid radially in each axial stage and the successive pressures would be added in the discharge pressure.

Centrifugal compressors of this invention may be used for delivering air under pressure to the intake ports of Diesel type internal combustion engines. They may be used as superchargers for aircraft engines and the like, with lower rotating speeds than are currently required in conventional superchargers.

I claim:

A compressor comprising a chamber, a body of lubricant in the chamber, a rotor rotatably mounted in the chamber, bearings for the rotor, a fluid intake at the center of the rotor, a porous material comprising a maze of small passages in the rotor between the center of the rotor and its periphery, means external of the rotor for maintaining a fluid pressure difference between the center of the rotor and its periphery, and pressure responsive means for directing lubricant from said body to the bearings.

ALLEN TRASK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 578,860 Clark Mar. 16, 1897 700,224 McRae May 20, 1902 740,151 Longdon Sept. 29, 1903 1,676,783 King July 10, 1928 1,860,944 Nougle May 13, 1932 2,272,746 Holm-I-Iansen Feb. 10, 1942 

